Historical Figures in Neuroscience: Donald Hebb

Essay Title: “A Historical Figure in the field of Neuroscience, Neurology or Psychology”

Donald Olding Hebb is truly a historical figure in the field of neuroscience, neurology and psychology. Hebb’s work, in particular his monograph The Organization of Behavior: A Neuropsychological Theory, provided a biological explanation for numerous psychological phenomena and revolutionized the aforementioned fields, a feat emphasized by his consequent nomination for the 1965 Nobel Prize for Physiology or Medicine [1]. However, what distinguishes Hebb from other exceptional scientists is that his influence is not solely limited to his research. His work as an educator inspired many prominent psychologists, including Brenda Milner, Ronald Melzack and Michael Posner, and stimulated changes in educational approaches, most notably in the childhood education of the underprivileged [1].

Born in Chester, Nova Scotia, Canada to a family of physicians, Hebb originally aspired to be a novelist, graduating from Dalhousie University in 1925 with a B.A. in English [2]. Afterwards, he began to write a novel while teaching at his old school in Chester but both endeavours ultimately failed, and Hebb worked as a farmer and labourer to survive. While doing so, he started reading the works of Sigmund Freud, which motivated Hebb to pursue his graduate studies in psychology at McGill University [1]. At McGill, inspired by Pavlov’s and Sherrington’s research, he wrote his M.A. thesis, Conditioned and Unconditioned Reflexes and Inhibition – these ideas were further developed through his doctorate work at the University of Chicago and Harvard University, where he received his PhD in psychology in 1936 [1]. However, it was only when he began to study the effects of brain surgery on human behaviour at the Montreal Neurological Institute where he connected his graduate studies in neurobiology to higher-order functions of the brain [3], publishing his hypothesis in 1949 in his revolutionary book, The Organization of Behavior: A Neuropsychological Theory.

In his book, Hebb presents his theory which has three postulates: the synapse, the cell assembly, and the phase sequence. Regarding the synapse, Hebb suggests that if an axon of neuron A is in close proximity to neuron B so that it can repetitively excite it, a growth process or metabolic change will take place in the cells so that the efficiency of neuron A exciting neuron B is increased [3]. And as a result, when groups of neurons consistently fire together, they form “cell assemblies” that continue to be active after the initial triggering event. A cell assembly thus can be seen as the neural representation of the initial triggering event itself [4]. Finally, Hebb proposed that complex behaviours, such as visual perception, are a result of connections between cell assemblies called “phase sequences” that can be activated by any of its constituent cell assemblies [5].

Hebb’s theory was monumental, inspiring the cognitivist revolution in psychology as research shifted its focus from human behaviour to its underlying mental processes [6]. Psychology increasingly began to rely on neuroscience, with much neuroscientific research using Hebbian theory as a foundation. And as a result, significant ideas in behavioural neuroscience emerged, ranging from perceptual development to synaptic modifiability [4]. The latter field in particular was especially key as it explained the biological foundations of learning and memory, with much research (e.g. long term potentiation) being applied in neurology and psychiatry to treat neurodegenerative diseases and addiction [7][8]. However, Hebbian theory’s sphere of influence stems beyond the biological sciences, extending to fields such as cognitive science and artificial intelligence. Acting as the fundamental mechanism behind artificial neural networks from their conception in the 1950s to the current models today [4], the applications of these networks span a wide variety of fields; ranging from mathematics (function approximation and statistics), to robotics and computing. Computing applications of neural networks have especially been important, as they have been instrumental in information technology (pattern recognition) [9], finance [10], medicine (diagnosis of cancer) [11], and even neuroscience (theoretical/computational neuroscience) [4]. Thus, it is evident that Hebbian theory has contributed to a plethora of academic disciplines, and provided the impetus for numerous advancements in science and technology.

Yet, Hebb’s contribution to academia is not confined by Hebbian theory; his extensive work on recovery from brain surgery, brain function localization, and the role of the environment in cognitive development were also noteworthy. Hebb’s research on brain function after brain surgery in epileptics with Wilder Penfield revealed the variation in cognitive regeneration with age. While removing a portion of the brain in adults lead to significant and catastrophic loss of brain function, in children there were almost no consequences [1]. From these findings, Hebb deduced the importance of external sensory stimulation in adult thought processes, which he experimentally demonstrated as sensory deprivation caused impaired function and hallucinations. Subsequently, studying localization of brain function with N. W. Morton, Hebb discovered preliminary evidence for the localization of visual recognition in the right temporal lobe and found the minimal effects on intelligence and personality of frontal lobe removal in epileptic patients, contrary to the contemporary evidence [1]. Enticed by this, Hebb hypothesized that the frontal lobe was only essential in early-life learning. Together with Kenneth Williams, he began to experiment on rats, blinding rats during different developmental stages and measuring their performance in a variable rat maze, the Hebb-Williams maze (which has since been used by numerous studies to test animal intelligence). Hebb found that the problem-solving skills that developed in the infant stages lasted until adulthood, which has since inspired studies in the role of the enriched environment in developmental neurobiology and psychology, and has been used to develop programmes (Head Start) to enrich the experiences of underprivileged children to promote maximal cognitive development [1].

Finally, Hebb’s work as an educator has had a substantial impact, both in teaching influential psychologists and promoting psychological research. Having taught in a variety of universities in Canada, Hebb inspired many students – the most notable being Brenda Milner [1]. Milner closely worked with Hebb as a graduate and doctorate student, and much of her research is inspired by Hebb’s work with neurosurgical patients. Her case report on HM, an epileptic treated with a bilateral medial temporal lobectomy who suffered from anterograde amnesia, and studies on the role of the frontal lobe in problem solving became landmark papers in neuropsychology [1]. Moreover, Hebb, as the department chair of psychology in McGill, promoted the scientific study of brain and behaviour, which aided in establishing the university as a centre for psychological and neuroscientific research [12].

From these achievements, it is clear that Donald Olding Hebb is a significant historical figure in the fields of neuroscience, neurology and psychology. His work revolutionized science and technology as a whole, and inspired many students that continued and survived his research. Whether it is in the software helping clinicians diagnose cancers, or the Head Start programmes helping the underprivileged, the legacies of his work are visible even to this day.